The present invention relates to a hydraulic control device.
There exists a hydraulic control device that supplies hydraulic oil to a vehicle driving apparatus such as an automatic transmission. Japanese Patent Application Publication No. JP-A-2006-291981, for example, describes a hydraulic control device of a hybrid driving apparatus. The hydraulic control device is equipped with two types of oil pumps, a mechanical oil pump and an electric oil pump, and generates hydraulic pressure by discharging hydraulic oil that has been taken in from an oil pan via a strainer from the oil pumps. The hydraulic pressure generated by the oil pumps is then adjusted to a predetermined line pressure by a pressure regulating valve and supplied to respective portions. Destinations to which the adjusted hydraulic pressure is supplied include lubricating oil passages of respective portions of the hybrid driving apparatus and control valves for controlling the operation of friction engagement elements. Destinations to which the adjusted hydraulic oil is supplied also include an oil cooler for cooling hydraulic oil.
Provided in the hydraulic control device is a check valve acting as a cooler bypass valve on an upstream side of the oil cooler. If the hydraulic pressure of the hydraulic oil supplied to the oil cooler is too high, then the cooler bypass valve is opened to drain the hydraulic oil. Accordingly, a structure is achieved in which excessive hydraulic pressure does not act on the oil cooler. In addition, the hydraulic control device is structured such that hydraulic oil that has passed through the oil cooler, hydraulic oil that was drained when the cooler bypass valve opened, and hydraulic oil supplied to the lubricating oil passages of respective portions are all discharged to the oil pan.